The invention relates to an electrical machine, especially to an electric motor.
When assembling such machines, a problem experienced towards the end of the assembly process is how to set the commutator, as simply and quickly as possible, between several brushes which are ordinarily resiliently urged toward the commutator. For this purpose normally the brushes are arrested in an assembly position a certain distance from the outer surface of the commutator so that the commutator can freely be set between the brushes. After the assembly of the armature the arrest is released so that the brushes can touch the outer surface of the commutator.
German specification DE-OS 33 28 683 shows an electric motor including a housing cover closed at its front side by a lid, a rotatable armature located within the housing, a commutator, and at least one brush located in a tube which is attached to a brush support plate. The brush is resiliently urged toward its operational position in contact with the commutator. A deflectable locking lug is provided to arrest the brush in an assembly position a certain distance from the commutator. In this specification two different possibilities are taught for deflecting the locking lug to release the arrest of the brushes.
In the first embodiment the housing cover comprises a recess at the level of the brush support plate through which a tool can be inserted after the assembly of the electric motor. By means of this tool the locking lug can be deflected aside to such an extent that it stays deformed and does not spring back into its assembly position. A disadvantage of this embodiment is that the housing wall must comprise an aperture which can only be closed in a further operational step afterwards and that an operational step is necessary for deflecting the locking lug.
In a second embodiment a projection extends the inner side of the housing cover which projection is pushed against the free end of the locking lug during the assembly and releases the arrest of the brushes itself. While this approach requires no aperture in the housing cover, the projection cannot easily be produced. Because the housing cover is normally rolled from a metal blank, forming the projection is especially difficult when design constraints require that it be on a joint or exterior edge of the cover.